Hanle detection for optical clocks

Considering the strong inhomogeneous spatial polarization and intensity distribution of spontaneous decay fluorescence due to the Hanle effect, we propose and demonstrate a universe Hanle detection configuration of electron-shelving method for optical clocks. Experimental results from Ca atomic beam optical frequency standard with 423 nm electron-shelving method show that a designed Hanle detection geometry with optimized magnetic field direction, detection laser beam propagation and polarization direction, and detector position can improve the fluorescence collection rate by more than one order of magnitude comparing with that of inefficient geometry. With the fixed 423 nm fluorescence, the improved 657 nm optical frequency standard signal intensity is presented. And the potential application of the Hanle detection geometry designed for facilitating the fluorescence collection for optical lattice clock with a limited solid angle of the fluorescence collection has been discussed. This Hanle detection configuration is also effective for ion detection in ion optical clock and quantum information experiments. Besides, a cylinder fluorescence collection structure is designed to increase the solid angle of the fluorescence collection in Ca atomic beam optical frequency standard.Comment: 5 pages, 6 figure

An Empirical Study on the Volatility based on SSE 50ETF

The rapid development of financial derivatives trading has a strong appeal to many investors. When investors are trading, it not only brings them profits but also brings risks. As an essential parameter of risk measurement, volatility has always been one of the core contents of financial research. On February 9, 2015, China’s financial market, the SSE 50ETF option as the first option is officially listed on the Shanghai Stock Exchange, which means that Chinese financial market entered into the age of options. There is no doubt that analyzes the volatility of this option is becoming a hot topic in China. This paper used three different types of data and the suitable calculation methods of volatility to conduct empirical research. As for the historical volatility, this paper using the SSE 50ETF daily return to calculate the return rate. The results of the historical volatility show that the volatility of SSE 50ETF is characterized by volatility clustering, the leptokurtosis and fat-tail, and anti-leverage effect. Secondly, as for the analysis of the realized volatility, choose the five-minute data at the trading day as the research data to establish the HAR-RV model. The results show that the volatility of SSE 50ETF has characteristic of long memory. Finally, for the implied volatility, the SSE 50ETF option data is selected and calculated volatility by using the dichotomy method based on the B-S pricing formula and weighted by options Vega value. The analysis showed that compared with call options, the relation curve between implied volatility and strike price of put options has distinct smile shape when the maturity is fixed. Moreover, when the strike price is fixed, the closer the contract is to maturity, the more intense the implied volatility would be, and the more dispersed the volatility would be. By comparing the empirical results of these three types of volatility, we find that they all have consistency in these features like leptokurtosis and fat-tail, leverage effect, long memory and volatility smile. Besides, the fluctuation trends of these three volatilities are similar and are also in line with financial market developments

Preparation and characterization of ZnO microcantilever for nanoactuation

Zinc oxide [ZnO] thin films are deposited using a radiofrequency magnetron sputtering method under room temperature. Its crystalline quality, surface morphology, and composition purity are characterized by X-ray diffraction [XRD], atomic force microscopy [AFM], field-emission scanning electron microscopy [FE-SEM], and energy-dispersive X-ray spectroscopy [EDS]. XRD pattern of the ZnO thin film shows that it has a high c-axis-preferring orientation, which is confirmed by a FE-SEM cross-sectional image of the film. The EDS analysis indicates that only Zn and O elements are contained in the ZnO film. The AFM image shows that the film's surface is very smooth and dense, and the surface roughness is 5.899 nm. The microcantilever (Au/Ti/ZnO/Au/Ti/SiO2/Si) based on the ZnO thin film is fabricated by micromachining techniques. The dynamic characterizations of the cantilever using a laser Doppler vibrometer show that the amplitude of the cantilever tip is linear with the driving voltage, and the amplitude of this microcantilever's tip increased from 2.1 to 13.6 nm when the driving voltage increased from 0.05 to 0.3 Vrms. The calculated transverse piezoelectric constant d31 of the ZnO thin film is -3.27 pC/N. This d31 is high compared with other published results. This ZnO thin film will be used in smart slider in hard disk drives to do nanoactuation in the future

First-principles Methodology for studying magnetotransport in magnetic materials

Unusual magnetotransport behaviors such as temperature dependent negative magnetoresistance(MR) and bowtie-shaped MR have puzzled us for a long time. Although several mechanisms have been proposed to explain them, the absence of comprehensive quantitative calculations has made these explanations less convincing. In our work, we introduce a methodology to study the magnetotransport behaviors in magnetic materials. This approach integrates anomalous Hall conductivity induced by Berry curvature, with a multi-band ordinary conductivity tensor, employing a combination of first-principles calculations and semi-classical Boltzmann transport theory. Our method incorporates both the temperature dependency of relaxation time and anomalous Hall conductivity, as well as the field dependency of anomalous Hall conductivity. We initially test this approach on two-band models and then apply it to a Weyl semimetal \CSS. The results, which align well with experimental observations in terms of magnetic field and temperature dependencies, demonstrate the efficacy of our approach. Additionally, we have investigated the distinct behaviors of magnetoresistance (MR) and Hall resistivities across various types of magnetic materials. This methodology provides a comprehensive and efficient means to understand the underlying mechanisms of the unusual behaviors observed in magneto-transport measurements in magnetic materials.Comment: 6 pages, 4 figure